Composition containing crystalline 1,2-polybutadiene

ABSTRACT

A RUBBER COMPOSITION CONSISTING ESSENTIALLY OF 3 TO 5O% BY WEIGHT OF A 1,2-POLYBUTADIENE HAVING A 1,2-ADDITION UNITS CONTENT OF 70% OR HIGHER AND CRYSTALLINITY OF 5% OR HIGHER, AND 97 TO 50% BY WEIGHT OF AT LEAST ONE CONJUGATED DIENE-BASED RUBBERY POLYMER SELECTED FROM THE GROUP CONSISTING OF STYRENE-BUTADIENE COPOLYMER RUBBER, POLYISOPRENE RUBBER, NATURAL RUBBER, ACRYLONITRILE-BUTADIENE RUBBE AND POLYCHLOROPRENE RUBBER. SAID RUBBER COMPOSITION HAS AN IMPROVED GREE STRENGTH, AND EXCELLENT EXTRUDABILITY, AND MOLDABILITY AND VULCANIZATES OBTAINED THEREFROM HAVE HARDNESS AND HIGH RSISTANCE TO OZONE AND WEATHERING.

United States Patent 3,827,991 COMPOSITION CONTAINING CRYSTALLINE1,2-POLYBUTADIENE Noriaki Ando, Yasuyuki Yaeda, and Isao Furuta,Yokkaichi, and Ryuichi Sakata, Kobe, Japan, assignors to Japan SyntheticRubber Co., Ltd., Tokyo, Japan No Drawing. Filed Mar. 12, 1973, Ser. No.340,128 Claims priority, application Japan, Sept. 11, 1972,

7/ 90,468 Int. Cl. C08c 9/04; C08f 29/14 US. Cl. 260- 11 Claims ABSTRACTOF THE DISCLOSURE This invention relates to a rubber composition havingimproved properties. More particularly, this invention relates to arubber composition comprising 1,2-polybutadiene and a conjugateddiene-based rubbery polymer and possessing an extremely high greenstrength, eX- cellent extrudability and moldability and a tendency toyield a vulcanizate of high hardness and of high resistance to ozone andweathering.

Rubbers for general uses which have hitherto been commerciallyavailable, particularly conjugated dienebased rubbers, have excellentrubbery properties such as low heat build-up, reduced permanent set, andyet high impact resilience, but, on the other hand, have such defects aslow green strength, inferior extrudability and moldability, and inferiorresistance of the vulcanizate to ozone and weathering.

In order to improve the green strength, there have hitherto beenproposed processes whereby a resinous polymer such as polyethylene isblended or chemicals such as nitroso compounds and phthalic anhydrideare incorporated. However, problems still remain in physical propertiesof the 'vulcanizate in the former process and in economical aspect inthe latter process.

1,2-Polybutadiene shows greatly different physical properties, dependingupon its crystallinity. It is possible, therefore, to vary the physicalproperties of 1,2-polybutadienes from rubbery to resinous by properlycontrolling the crystallinity. The method of controlling thecrystallinity has already been established in US. Pat. 3,498,963 and3,522,332. The thus obtained 1,2-polybutadiene having a 1,2-additionunits content of 70% or higher and crystallinity of 5% or higher hasproperties intermediate between rubber and resin.

As a result of an extensive study, the present inventors have found thatby incorporating the above-mentioned 1,2-polybutadiene into a conjugateddiene-based rubbery polymer there can be obtained a rubber compositionwhich is greatly high in green strength, is excellent in extrudability,moldability and surface appearance after treatment, and tends to yieldavulcanizate possessing high hardness and high resistance to ozone,without imparing the characteristics of the conjugated diene-based3,827,991 Patented Aug. 6, 1974 "ice rubbery polymer, such as low heatbuild-up, low permanent set, high impact resilience.

This invention provides a rubber composition consisting essentially of 3to 50% by weight of 1,2-polybutadiene having a 1,2-addition unitscontent of or higher and crystallinity of 5% or higher, and 97 to 50% byweight of at least one conjugated diene-based rubbery polymer selectedfrom the group consisting of styrenebutadiene copolymer rubber,polyisoprene rubber, natural rubber, acrylonitrile-butadiene copolymerrubber and polychloroprene rubber.

The 1,2-polybutadiene to be used in this invention is that having a1,2-addition units content of 70% or higher, preferably or higher, andcrystallinity of 5% or higher, preferably 5 to 50%, especiallypreferably 5 to 30% in view of the ease of incorporation. Its molecularweight can be selected from a wide range, so both liquid and solidpolymers may be used though it is preferable to use a polymer having anintrinsic viscosity [1;] of 0.7 dL/g. or higher (determined in tolueneat 30 C.). When the 1,2-addition units content is below 70%, the tensilestrength and tear strength will be markedly low. When the crystallinityis below 5%, it is impossible to obtain the result expected in thisinvention.

In this invention, the conjugated diene-based rubbery polymers may beused alone or in combination of two or more.

In this invention, the method of blending the aforesaid1,2-polybutadiene with a conjugated diene-based rubbery polymer has noparticular restriction. Both solutions of the respective components canbe mixed with each other followed by removing the solvents, oralternatively, both components in the form of solids can be blended witheach other by a conventional method, for example, by means of roll,Banburys mixer or kneader to obtain a similar result.

The amount of 1,2- polybutadiene to be blended is 3 to 50%, preferably 5to 50% by weight. If the amount exceeds 50% by weight, the heat build-uppermanent set or impact resilience will be adversely affected, while ifit is less than 3% by weight, no substantial merit of this inventionwill be obtained.

It is, of course, possible to further incorporate into the rubbercomposition of this invention at least one conventional compoundingingredient, such as reinforcing agents, fillers, extender oils,pigments, vulcanizing agents, vulcanizing accelerators, vulcanizingactivators, antioxidants, ultraviolet absorbers, blowing agents,odorants, softening agents, etc.

The rubber composition obtained according to this invention possesses ahigh green strength, excellent extrudability, and excellent moldabilityand in addition, a vulcanizate therefrom has a high hardness andexcellent resistance to ozone and weathering.

The invention is further explained below in more detail with referenceto examples which are not by way of limitation but by way ofillustration.

The characteristic properties of 1,2-polybutadienes used in the examplesare as follows:

The micro-structure of the above-noted polybutadienes was measured bythe infrared absorption spectrum method of D. Morero et a1. [Chimie etInd., 41, 758 (1959)]. The crystallinity was determined by the densitymeasurement method in which the following equation was used:

where d density of the specimen measured at 20 C., d density of thecrystalline region,

d density of the amorphous region, and

X: crystallinity in percent.

The value of d used was that of the crystalline 1,2- polybutadienecalculated by Natta from X-ray experiments to be 0.963 [L. G. Natta, J.Polymer Sci., 20, 251 (1956)]. The value of d, used was 0.892, or thedensity of the 1,2-polybutadiene obtained by the synthesizing processproposed in US. Pat. 3,498,963.

TABLE 1 Sample number Compounding ingredients (partsbywt.) 1 2 3 4 5 6 7A B D 1,2-polybutadleno 0 10 3O 10 10 30 Styrene-butadiene rubber (JSR1500*) 100 90 90 70 90 70 Carbon black (HAF) Process oil (high aromatictype) Zine oxide.

Stearic acid-.. Antioxidant (N-1s0p1opy pheny p-phenylenediamine) 1Accelerator CZ (N-cyclohexyl-Z- benzothiazyl sulfenamide) 0. 8 Sulfur 1.

1 Comparative example. *Manufactured by Japan Synthetic Rubber (30.,Ltd.

Measurements were made on the resulting compositions for green strengthand extrudability, and on the vulcanizates of the compositions forphysical properties and ozone resistance. The results obtained were asshown in Table 2.

TABLE 2 Item of test Green strength: l

Sample number At room temperature:

Tensile strength, kgJcmfl. lg lorgation, percent At l Elon

Tensile strength, kgJcmfi. longation, percent Tensile strength,kgJcmflgation, percent E Extrutlability 2 Rate of extrusion, cc./min Dieshrinkage, percent Die swelling, percent.--... Physical properties ofvulcanizate: 3 300% modulus, kgJcmfl--- Tensile strength, kgJemJ.Elongation, percent.-- Hardness, JIS Hs Ozone resistance: 4

After- 1 hour C-2 B-2 A-l B-2 11-1 13-2 A-l 3 hours- 0-2 B-2 A-2 B 2 A-Z13-2 A-Z 10 hours (3-3 13-3 A3 B A-3 13-3 A-3 24 hours 0-4 13-4 A4 A-4B-4 A-4 48 hours- 0-4 13-4 A4 13- A-4 13-4 A 5 96 hours 0-5 13-5 A5 B- 5A-5 13-5 A- l 118 K-630l (J IS is an abbreviation of Japanese IndustrialStandards.)

a ASTM D 223M323. Cond tions of extrusion: Barrel temperature, 70 0. dietemperature, 0. Number of revolutions of the sorew: 21 r.p.m.

8 Measured on the vulcamzate obtained by vulcanizing at C. for 30minutes (JIS 4 ASTMD 1149454 (J IS K6301). Conditions of measurement:40C, ozone concentration, 50 p.p.h.m.; stretch ratio, 20% Method ofevaluation: Numb er of cracks-A, a small numb er B, many;

0, innumerable. Size and depth of cracks: 1, invisible to the naked eye,but

recognizable with a magnifying lens (10X); 2, recognizable with thenaked eye; 3, deep and relatively large cracks (less than 1 mm.); 4,deep and large cracks (from 1 mm. to 3 mm.); 5, more than 3 mm. cracksor cracks almost leading to cutting.

a Comparative example.

EXAMPLE 1 Mixtures in accordance with the compounding recipes (parts byweight) shown in Table 1 were blended by Banburys mixer to obtain rubbercompositions.

EXAMPLE 2 Mixtures prepared in accordance with the compounding recipes(parts by weight) shown in Table 3 were blended -by Banuburys mixer toobtain rubber compositions.

TABLE 3 Sample number Compoundingingredient (parts by wt.) 8 9 10 11 1213 14 15 16 tttfiltttitt ififif styrene butadiene rubber (J S R 1500)cis-Poly1soprene rubber (Natsyn 2200) Carbon black (HAF 50 50 so Processoil thigh aromatic type) 10 5 10 Zinc mride 3 3 3 Stearic 2 2. 5 2Antioxidant (N-isopropyLN-phenyl-pphenylenediamine) 1 1 1 Accelerator CZ(N-eyclohexyl-Z-benzothiazylsu1fenamide) 0. 8 O. 8 0. 8 Suliur- 1. 75 2.0 1. 75

1 Comparative example.

' Manufactured by Goodyear Tire & Rubber 00., Ltd.

EXAMPLE 4 Injection curing was carried out on the rubber compositions ofsample Nos. 17, 18 and 19 in Table 5 of Example 3 by means of aconventional injection molding machine. The results obtained were asshown in Table 7.

TABLE 4 Sample number Item of test 8 B 9 10 11 12 a 13 14 15 16 Greenstrength: l

At room temperature:

50% modulus, kg./om. 4. 7 5. 5 8. 5 17.3 2. 8 3. 6 7. 5 18.0 16. 5 100%modulus, kgJcm. 4. 3 5. 5 9.2 23. 7 2. 6 3. 5 8. 9 23. 3 17. 0 Tensilestrength, kgJcm. 4. 8 5. 9 10. 6 35. 0 2. 9 3. 7 9. 8 29. 9 l5. 5 At l llopgau'on, percent 670 490 550 310 1, 700 1, 700 1,150 410 540 Tensilestrength, kgJcm." a. 5 4. 2 7.8 19.1 2. 4 2. 9 4. e 1e. 1 11.1 At 8gloggation, percent 370 350 230 250 370 440 440 500 300 Tensile strength,kgJem. 1. a 1. 7 2. 2 3. 3 1. 4 1. 4 2. a 4.1 a. o Elongation, percent370 260 260 220 340 320 290 270 300 Extrudability: 2

Rate of extrusion, ccJmln 188. 3 197. 1 192.0 Die shrinkage, percent 44.2 44. 0 43. 4 Die swelling, percent 79. 2 78.6 76. 7 Physical propertiesof vulcanizate: 3

300% modulus, kgJcm. 70 73 89 Tensile strength, kgJcm? 232 224 226Elongation, percent 740 720 680 Hardness, JIS Hs 63 65 70 Impactresilience, percent 53 V 52 50 Compression permanent set, percent 23 2428 1 The same as in Table 2. 1 The same as in Table 2. 3 The same as inTable 2.

Comparative example.

EXAMPLE 3 The mold used was a cylindrical mold, 100 mm. in di- Mixturesprepared in accordance with the compound recipes (parts by weight) shownin Table 5 were blended by Banburys mixer to obtain rubber composition.

TABLE 5 Sample number Compounding ingredient (parts by wt.) 17 1 18 191,2-Polyb1itadiene E O 10 20 eis-Polyisoprene rubber (Natsyn 2200) 10090 80 Transparent zinc oxide 3 Stearic acid 2 Process oil (naphthemcoil)..... White carbon (hydrous s1hca) 15 Antioxidant(2,6-di-t.-butyl-p-cresol) 1. 5 Antiogone-craok agent (Sunnoc; selectedspecial 0 5 wax Peptizer (zinc 2-benzamidothiophenate) 0.5 Sulfur 1.8Accelerator (mercapto benzothiazole) 1. 6 Accelerator(tetramethylthiuram dlsulfide) 0. 4

1 Comparative example.

" Manufactured by Ohuchi Shinko Kagaku Kogyo Co., Ltd.

Measurements were conducted on the resulting compositions for Mooneyviscosity and mold flow characteristics and on the vulcanizates of thecompositions for physical properties. The results obtained were as shownin Table 6.

TABLE 6 Sample number 1 T. Arai. "A Guide to the Testing of RheologicalProperties with Koka Flow Tester", Maruzen, Tokyo (1958).

2 Measured on vulcanizate obtained by presscurmg the composition at 160C. for 15 minutesv Comparative example.

ameter, 400 mm. in length, and 0.5 mm. in thickness, provided with aninjection gate on the top of one end of the cylinder. The injectionpressure was kg./cm. and curing was effected at 170 C. for 4 minutes.

What is claimed is:

1. A rubber composition consisting essentially of 3 to 50% by weight ofa 1,2-polybutadiene having a 1,2-addition units content of 70% or higherand crystallinity of 5% or higher, and 97 to 50% by weight of at leastone conjugated diene-based rubbery polymer selected from the groupconsisting of styrene-butadiene copolymer rubber, polyisoprene rubber,natural rubber, acrylonitrilebutadiene copolymer rubber andpolychloroprene rubber.

2. A rubber composition consisting essentially of 3 to 50% by weight ofa 1,2-polybutadiene having a 1,2-addition units content of 70% or higherand crystallinity of 5% or higher, and 97 to 50% by weight of at leastone conjugated diene-based rubbery polymer selected from the groupconsisting of styrene-butadiene copolymer rubber, polyisoprene rubberand natural rubber.

3. A rubber composition according to Claim 1, wherein the1,2-polybutadiene has a 1,2-addition units content of or higher.

4. A rubber composition according to Claim 2, wherein the1,2-polybutadiene has a 1,2-addition units content of 85% or higher.

5. A rubber composition according to Claim 1, wherein the1,2-poiybutadiene has a crystallinity of 10 to 50%.

6. A rubber composition according to Claim 2, wherein the1,2-po1ybutadiene has a crystallinity of 10 to 50%.

7. A rubber composition according to Claim 3, wherein the1,2-polybutadiene has a crystallinity of 10 to 50%.

8. A rubber composition according to Claim 4, wherein the1,2-polybutadiene has a crystallinity of 10 to 50%.

9. A rubber composition according to Claim 1, wherein the amount of the1,2-polybutadiene is 5 to 30% by weight.

10. A rubber composition according to Claim 1, wherein the1,2-polybutadiene has an intrinsic viscosity of 0.7 dL/g. or higher(determined in toluene at 30 C.).

11. A rubber composition according to Claim 2, wherein the1,2-polybut-adiene has an intrinsic viscosity of 0.7 dL/g. or higher(determined in toluene at 30 (3.).

References Cited UNITED STATES PATENTS 3,696,062 11/1972 Lesage et a1.260'5 MURRAY TILLMAN, Primary Examiner J. ZIEGLER, Assistant ExaminerUS. Cl. X.R.

2602.5 L, 33.6 AQ, 41.5 A, 890, 894

